This invention relates to a one-bath etching method for processing a gravure plate, and a device which, in order to etch a gravure plate according to a variable rotational speed one-bath etching method, the permeation characteristic of a resist layer is obtained in advance, thereby to provide most suitable etching conditions before the etching operation.
A gravure plate processing one-bath etching method is excellent in etching control. In the method, while a ferric chloride solution having a predetermined density is being supplied to the cylinder surface, the cylinder rotational speed is varied, so that an aimed cell depth curve is obtained. In the conventional method, during etching, the cell depths of the shadow-most portion and a desired portion are detected, and whenever the cell depth of the desired portion coincides with an intermediate set value, the cell-depth of the shadow-most portion is measured, so that when the depth thus measured is larger than a predetermined value, the rotational speed is decreased, and when smaller, the speed is increased, to adjust the cell depth.
Thus, the conventional method can control the cell depths at only two points. Therefore, agreement of the cell depths of half-tone portions cannot be detected until the etching operation is finished.
The above-described conventional method is of the feedback control type, and accordingly needs a cell depth sensor and an arithmetic control unit. Thus, the etching machine is necessarily intricate in construction.